The present invention relates to a device for withdrawing body liquids and transferring them into sample tubes.
Devices have been known for some time comprising a rigid protection cap defining a concavity, and a thin sharp-ended steel tubular stem screwed to the cap until it projects into its concavity.
The tubular stem is connected to means for penetrating the human body, in particular to an elastic flexible tube fixed to a foldable butterfly needle, or directly to an injection needle.
The device is suitable for use in withdrawing blood in combination with sample tubes to be inserted into the cap concavity and having their interior chamber under vacuum and closed by a yieldable elastomeric plug capable of sealing the aperture produced by the tubular needle stem (the plug being penetrated by the tubular needle stem and then sealing the channel produced by the tubular stem when the latter is extracted).
In use, the butterfly needle is inserted into a patient's vein, after which a sample tube is inserted into the cap such that the plug in the cap is traversed by the point of the tubular stem located within the cap. The vacuum present in the sample tube draws blood into the sample tube.
Hence the blood is drawn into the sample tube by an operation which is immediate and protected by virtue of the presence of the cap surrounding the point of the tubular stem.
After use the tubular stem is removed from the cap (which is reused) and disposed of in appropriate safety containers dedicated to needle collection.
Said operation carries however the risk that once separated from the cap, the tubular stem (which is soiled with the patient's blood) can prick the operator as its point is no longer enclosed by the cap.
A further drawback lies in the fact that in flowing into the sample tube, in particular in passing through the connection points between the tubular stem and its support member and between this latter and the external flexible conduit (or needle), the blood tends to "hemolyze", ie to break down its hemoglobins, so altering certain of its characteristics.
Moreover the tubular stem requires a valve which prevents the blood passing unless the the tubular stem is applied to a sample tube. The valve currently used consists substantially of a soft rubber cap enclosing the entire tubular stem.
Said valve has however various drawbacks.
A first drawback is that after the rubber cap has been penetrated a few times (to feed the blood into the sample tube) by the point of the tubular stem, it loses its sealing property and allows the blood to drip.
A further drawback is that the blood remaining in the cap inevitably soils the outer surface of the sample tube plug when the tubular stem is inserted through it.